Pebeo Drawing Gum is a quality masking fluid. It can be applied using a brush, nib or ruling pen.If you are using a brush to apply the drawing gum it must be cleaned immediately afterwards as the fluid is waterproof when dry and could spoil the brush. It is a good idea to use an old brush.Because the masking fluid can be used in nibs, it offers many calligraphic possibilities. A popular technique is to produce some calligraphy using the drawing gum as ink. Remember to immediately wash the nib in warm soapy water. Leave the masking fluid to dry completely otherwise the paint will get under the mask. Next, a watercolour wash is applied over the lettering. Once the wash is dry the drawing gum be carefully removed. Do this by gently rubbing the mask with your finger or a clean eraser.